In various industries it is necessary, after a component has been manufactured or assembled, to carry out a degassing step under vacuum, this degassing step causing volatile chemical species trapped by this component to desorb. This degassing step is of particular importance in the space field, notably because liberation of chemical species in extra-atmospheric space is associated with a high risk of damage to and contamination of constituents of the spacecraft. Thus, with the aim of ensuring the integrity of equipment such as optical or telecommunication systems for example, it is necessary to degas the components or subsystems of a satellite such as an inertial measurement unit, a solar array drive mechanism, or even the fully assembled satellite platform. Provision is generally made for a number of degassing steps throughout the manufacturing process of the satellite. For example, a composite will be degassed once after its production, a second time after it has been integrated in an operational subsystem, then once more after the final assembly of the satellite.
To carry out these degassing operations various vacuum chambers are used, the capacity of which may vary from one meter cube to as much as typically 500 m3, these chambers also being capable of being heated to temperatures typically comprised between room temperature and 150° C. for vacuum pressures typically comprised between 10−5 and 10−7 hPa. Knowing that said degassing operations generally last one to three days, the high industrial cost that such operations represent will be readily apparent.
Depending on the constituent materials of the component or subsystem in question, various volatile chemical compounds are liable to be liberated. For example, in the space field, during the degassing of the insulating product known as multilayer insulation (MLI) or the solar array drive mechanism (SADM), various solvents, water and/or silicon-containing products may be liberated during a thermal vacuum degassing operation.
The degassing processes used at the present time are simple. They generally consist in keeping the component in a vacuum chamber under empirically set vacuum, temperature and time conditions. Thus various protocols have been defined that are applied depending on the component or subsystem in question. By way of example, typically implemented protocols include:                24 hours at 120° C.,        48 hours at 100° C., or        72 hours at 80° C.,for a final vacuum level of about 10−6 hPa.        
However, these values are entirely empirical and sometimes based on outdated studies. These degassing operations do not allow the effectiveness of the degassing to be measured during the test. It is therefore possible, under these conditions, for the test to continue several hours after the degassing limit has been reached, or inversely, at the end of the test, for the degassing not to have been completed effectively.
One known technique for measuring the effectiveness of a vacuum degassing operation implements instruments of the quartz balance type. Quartz balances do indeed allow a satisfactory quantitative measurement to be obtained when the mass of the collected deposit remains small in size. These instruments have been employed with success when the equipment to be degassed is an optical system or a system having a low volatile compound content. In contrast, when the equipment to be degassed liberates a large amount of or more contaminating volatile compounds, these instruments reach their limits. In particular, they rapidly saturate and then require regular regenerating operations to degas them. This need for regular regeneration in order to obtain once more a measurement of the deposited mass makes these instruments unsuitable for measuring the effectiveness of the degassing of components employed in the space field. Another difficulty with this technique relates to the precision of the measurement when the temperature of the degassing chamber is very different from the temperature of the boat serving to collect the deposit. In order to make it possible for the volatile compounds to be analysed to condense, the quartz balance then plays the role of a too-effective cold trap; it then rapidly saturates meaning that it must frequently be regenerated. Imprecise measurements result that are unsuitable for effective following of degassing rate during a test.
The challenge is to provide a complete and rapid degassing operation, allowing the length and therefore the cost of the operation to be decreased, and subsequent steps of design or use to be made safe. The techniques currently employed are unsuitable for meeting this need. At the present time it would be desirable to provide a means allowing in real time, during the degassing operation, the degassing rate of a component placed under thermal vacuum to be followed.